I have seen this cam system develop from design to testing as the Helical Cam place is near where I live. It runs and performs just as you see it on the website - the fuel savings at part throttle are amazing but as HC themselves say - it may not be quite so spectacular with a full-size EFI engine.
As you say it won't fit a 4AGE Toyota. The head layout has to be something like the Nissan SR series of engines - which has slightly unusual valve gear - four lobes on each cam, forked finger followers etc. I have been told by HC that they are planning to build a system to fit the SR series engine. If I remember correctly - the SR puts out a bit more power than the equivalent inverted bucket type of Nissan engine. Realistically I think any engine with the HC would have to have a new head with something like the Nissan SR/SuzukiGSX valve gear layout.
As you say it won't fit a 4AGE Toyota. The head layout has to be something like the Nissan SR series of engines - which has slightly unusual valve gear - four lobes on each cam, forked finger followers etc. I have been told by HC that they are planning to build a system to fit the SR series engine. If I remember correctly - the SR puts out a bit more power than the equivalent inverted bucket type of Nissan engine. Realistically I think any engine with the HC would have to have a new head with something like the Nissan SR/SuzukiGSX valve gear layout.